Stevens stopped short of calling for an end to the death penalty, but he said there are many problems in the way it is used.

Recent exonerations of death row inmates through scientific evidence are significant, he told the American Bar Association, “not only because of its relevance to the debate about the wisdom of continuing to administer capital punishment, but also because it indicates that there must be serious flaws in our administration of criminal justice.”

He said the jury selection process and the fact that many trial judges are elected also work against accused murderers. He also said that jurors might be improperly swayed by victim-impact statements.

In recent years Stevens has been influential in votes that barred states from executing mentally retarded killers and those who were juveniles when they committed their crimes.